QSM (Quantitative Susceptibility Mapping) is known as a technique of calculating magnetic susceptibility of each tissue from phase signals included in an image acquired by an MRI apparatus. QSM can be interpreted as one of biomarker imaging techniques in which an index of a biological condition and a specific disease condition are imaged. Mapping of magnetic susceptibility of each tissue enables diagnosis of disease related to iron and ferrugination. For example, it is said that an abnormal region in Alzheimer's disease or multiple sclerosis causes the ferrugination. Such a ferrugination region in the brain can be identified by QSM.
Additionally, since an intracerebral bleeding area and a calcified area are difficult to discriminate from each other in an image acquired by a conventional MRI apparatus, thus, a CT (Computed Tomography) apparatus has been mainly used for discriminating an intracerebral bleeding area and a calcified area from each other.
Meanwhile, it is known that magnetic susceptibility of lime becomes minus and magnetic susceptibility of blood becomes plus, when magnetic susceptibility of water is set to be zero as a reference. Thus, an intracerebral bleeding area and a calcified area can be discriminated from each other by performing QSM on an image obtained by an MRI apparatus, which has an advantage of involving no X-ray exposure over a CT apparatus.